The invention relates to improvements in methods and apparatus for the separation and classification of a solids liquid slurry by a centrifugal separator which centrifugally separates the slurry into a light phase fraction and a heavy phase fraction.
In German Published Application 36 20 912, there is disclosed a solid bowl worm centrifuge for separating solids and liquid mixtures whereby the mixture within the drum is moved in one direction by a worm within the conveyor in co-current flow. The liquid is separated from the solids under influence of the centrifugal force. The liquid separated from the solids within the drum is subsequently accepted by channels arranged uniformly distributed over the circumference at the worm member and is discharged to the outside via discharge openings at one end. With the solids liquid mixture moving from left to right in a co-current flow within the drum, the liquids are discharged at the left hand side whereas the solids are discharged at the right hand side via nozzles which are uniformly distributed over the circumference at the right hand side of the centrifuge drum.
The liquids separated from the solids, with said liquids representing the light phase, are deflected by 180.degree. within the centrifuge drum in the proximity of the thick matter discharge and said liquid is transported through the drum discharged toward the outside through the channels arranged at the worm member and in a direction opposite that of the solids. Due to the substantial deflection of the light phase in the discharge region of the heavy phase, turbulences occur that do not favor a clear separation or classification of the solids liquid mixture and such turbulences are unavoidable in the region of the drum.
U.S. Pat. No. 3,782,623 discloses a solid bowl worm centrifuge for separating a solids liquid mixture. In that disclosure, the solid liquids mixture in the drum is essentially conducted in a co-current flow and the phases which are separated from another are discharged from the drum at the side lying opposite the material input side. In this disclosure, the light phase is deflected radially inwardly into the hollow shaft of the worm with the assistance of a curved pipe and is discharged to the outside through the hollow shaft of the worm. Turbulences within the centrifugal drum in this region are also unavoidable and do not favor enabling a clear separation particularly where a good separation or classification of the solids liquid mixture must occur. The same problem is true for known trailing blade centrifuges wherein the heavy phase in the centrifuge drum is radially inwardly accepted into the hollow shaft of the worm and is discharged toward the outside through this hollow shaft.
An object of the present invention is to provide an improved method and apparatus for the centrifugal separation and classification of a solids liquid mixture in a solid bowl worm centrifuge which avoids the disadvantages of arrangements heretofore available in the prior art.
A further object of the invention is to provide an improved solid bowl centrifugal separator wherein the slurry being separated moves coaxially from a first entry end toward a second entry end and separation occurs without the resulting distracting turbulence which occurs in devices heretofore available.
A still further object of the invention is to provide an improved centrifugal separator wherein separation occurs with a mechanism of an improved simplified structure to effect improved separation and improved throughput for equipment of a given size.